ML19277E336
| ML19277E336 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 10/09/2019 |
| From: | John Hickman Division of Decommissioning, Uranium Recovery and Waste Programs |
| To: | Sauger J Energy Solutions |
| Hickman J | |
| References | |
| Download: ML19277E336 (6) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 October 9, 2019 John Sauger Executive Vice President EnergySolutions 2701 Deborah Ave.
Zion, IL 60099
SUBJECT:
ZION NUCLEAR POWER STATION UNITS 1 AND 2 - REVIEW OF REVISED FINAL STATUS SURVEY REPORT - PHASE 1
Dear Mr. Sauger:
By letter dated November 1, 2018 (Agencywide Documents Access and Management System
[ADAMS] Accession No. ML18331A015), you submitted Final Status Survey Report (FSSR) - Phase 1. The staff responded by letter dated March 22, 2019 (ML19079A359), and identified certain issues which needed to be corrected before the report can be approved. On May 14, 2019, you provided responses to the issues we identified (ML19136A045). By letter dated June 21, 2019 (ML19178A106), you submitted Revised FSSR - Phase 1.
The staff has reviewed Revised FSSR - Phase 1 for Survey Units 10205, 10219A, 10219B, 10220C, 10222, 10223, 10224, and 10301, and the results presented are all a fraction of the Operational Derived Concentration Guideline Level (OpDCGL) for surface soil. The gamma walkover scanning coverage described in the report was adequate, and scan alarms which were investigated found no residual radioactivity above the OpDCGL. However, results from survey unit 10223 appear to have triggered the licensees commitment from Section 5.7.1.6.2 of the LTP (Revision 2) to assess subsurface residual radioactivity when 75 percent of the subsurface OpDCGL is detected in a surface soil sample. An investigation of subsurface residual radioactivity in survey unit 10223 will need to be conducted in accordance with the approved LTP. Based on the survey results provided to date, the survey units documented in Revised FSSR - Phase 1 10205, 10219A, 10219B, 10220C, 10222, 10224, and 10301 are acceptable to support release of those areas for unrestricted use.
Further details on our review are provided in the enclosed safety evaluation including some areas where improvements should be considered for future surveys.
In accordance with Title 10 of the Code of Federal Regulations section 2.390 of the U.S.
Nuclear Regulatory Commissions (NRC) Agency Rules of Practice and Procedure, a copy of this letter will be available electronically for public inspection in the NRC Public Document Room or from the Publicly Available Records component of NRCs ADAMS. ADAMS is accessible from the NRC Web site at http://www.nrc.gov/reading-rm/adams.html.
J.Sauger 2
If you have any questions, please contact me at 301-415-3017 or via e-mail at John.Hickman@nrc.gov.
Sincerely,
/RA/
John B. Hickman, Project Manager Reactor Decommissioning Branch Division of Decommissioning, Uranium Recovery and Waste Programs Office of Nuclear Material Safety and Safeguards Docket Nos. 50-295 and 50-304 and 72-1037
Enclosure:
Safety Evaluation by Office of Nuclear Material Safety and Safeguards cc: Zion Service List
- via e-mail OFFICE DUWP DUWP DUWP DUWP DUWP NAME JHickman CHolston* JClements* BWatson JHickman DATE 10/ 4 /19 10/ 4 /19 10/ 8 /19 10/8/19 10/9/19
Enclosure SAFETY EVALUATION BY OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS RELATED TO REVISED FINAL STATUS SURVEYS FOR PHASE 1 FACILITY OPERATING LICENSE NOS. DPR-39 AND DPR-48 ZIONSOLUTIONS, LLC ZION NUCLEAR POWER STATION UNITS 1 AND 2 DOCKET NOS. 50-295 AND 50-304
1.0 INTRODUCTION
By letter dated November 1, 2018 (Agencywide Documents Access and Management System
[ADAMS] Accession No. ML18331A015), ZionSolutions (ZS, the licensee) submitted Final Status Survey Report (FSSR) - Phase 1. The U.S. Nuclear Regulatory Commission (NRC) staff responded by letter dated March 22, 2019 (ML19079A359), and identified certain issues which needed to be corrected before the report can be approved. On May 14, 2019, ZS provided responses to the issues we identified (ML19136A045). By letter dated June 21, 2019 (ML19178A106), ZS submitted Revised FSSR - Phase 1. The licensees Final Status Survey (FSS) design criteria, implementation of the Data Quality Objectives (DQO) process, and survey approach/methods were reviewed, and final results were assessed against the licensees approved release criteria.
2.0 EVALUATION The Phase 1 FSS Final Report encompasses open land area surface soils. The Phase 1 Final Report specifically addresses eight (8) open land area survey units that total approximately 197,101 m2 in area as listed below.
Survey Unit Name Class Size (m2) 10205 Switchyard 3
54,573 10219A Area Far South of Switchyard (A) 3 2,433 10219B Area Far South of Switchyard (B) 3 7,516 10220C Adjacent to South Restricted Area - Lakeshore 3
27,870 10222 North Beach Area 3
21,778 10223 Power Block Beach Area 3
12,371 10224 South Beach Area 3
14,608 10301 West Training Area 3
55,942 The FSS results demonstrated that any residual radioactivity remaining in the survey units addressed by this Phase 1 Final Report resulted in a Total Effective Dose Equivalent (TEDE) to an average member of the critical group (AMCG) that does not exceed 25 mrem per year, and the residual radioactivity has been reduced to levels that are as low as reasonably achievable (ALARA). FSS activities essential to data quality were implemented
2 and performed under approved procedures. Trained individuals, using properly calibrated instruments and laboratory equipment that are sensitive to the suspected contaminants, performed the FSS of the Phase 1 survey units. The survey data for all Phase 1 survey units demonstrate that the dose (TEDE) from residual radioactivity is less than the maximum annual dose (TEDE) which corresponds to the release criterion for license termination for unrestricted use specified in 10CFR20.1402 and support the release of these areas from the 10CFR50 license. However, the licensee has committed to utilize an Operational Derived Concentration Guideline Level (OpDCGL) for survey planning and implementation. This OpDCGL value is lower than the Base Case DCGL (BcDCGL), which correlates to a TEDE of 25 mrem per year to an AMCG. Based upon the licensees commitment in Section 5.7.1.6.2 of the LTP (Revision 1) to assess subsurface residual radioactivity when 75 percent of the subsurface OpDCGL is detected in a surface soil sample, it appears that additional investigation is warranted in at least one survey unit. Information on this commitment and other comments to consider for future surveys are provided below.
3.0 COMMENTS In multiple release records, there is a discussion of a retrospective power curve, and a software output screenshot is shown in Attachment 5. NRC staff noted that in several cases the input shown appears to utilize previously obtained characterization results to calculate the standard deviation (sigma) rather than actual observed final status survey (FSS) results. NRC staff also noted that on more than one occasion the sigma input value appeared to be generically set to a sigma of 0.01, which did not appear to match standard deviation results in the report. MARSSIM Appendix I.9 provides guidance on performing retrospective power analyses by using the standard deviation observed during FSS and the number of samples taken. Software such as COMPASS or Visual Sample Plan may also be used to calculate the retrospective power curve. It is worth noting that MARSSIM states when the null hypothesis is rejected, the power of the test becomes a somewhat moot question, but that nonetheless, even in this case, a retrospective power curve can be a useful diagnostic tool and an aid to designing future surveys.
Based upon the licensees commitment in Section 5.7.1.6.2 of the LTP (Revision 2) to assess subsurface residual radioactivity when 75 percent of the subsurface OpDCGL is detected in a surface soil sample, it appears that samples in Survey Unit 10223 would have triggered this commitment for Sr-90, and a subsurface investigation should occur.
NRC staff also noted that none of the Sr-90 MDC values shown for Survey Unit 10223 are sufficient to detect Sr-90 at 75 percent of the subsurface OpDCGL. This becomes an important consideration for future FSSs where remediation may have been performed at subsurface depths.
With respect to detection sensitivities and MDCs, the licensee should consider that MARSSIM defines the critical level (LC), as the lower bound on the 95 percent detection interval defined for LD and is the level at which there is a 5 percent chance of calling a background value greater than background. MARSSIM also notes that this value should be used when actually counting samples or making direct radiation measurements, and that any response above this level should be considered as above background (i.e., a net positive result). While the licensee has only committed to re-evaluate surrogate ratios when both the surrogate and inferred radionuclides are detected above an MDC, it may be prudent to investigate hard-to-detect (HTD)
3 radionuclides further when HTD results are detected above the LC, rather than the MDC, as this indicates the potential for unrealized HTD contamination. The NRC staff notes that during the review of the LTP much consideration was given to the need for continuing characterization. Particular consideration was given to continuing characterization of HTD radionuclides, as only 9 soil samples were measured for HTDs during the sites pre-FSS characterization efforts. NRC staff will continue to look closely at HTD results during FSS.
References are made in the release records to an Attachment 14, FSS Field Log, but the attachment was not found in the submittals.
The licensee should be clearer about the actual scan investigation levels utilized in the field, as there appears to be a discrepancy between investigation level descriptions within release records. For example, release records indicate that the action level for investigation in a Class 3 open land survey unit is 50 percent of the OpDCGL, but there is a notation at the bottom of Table 13 (Synopsis of Scan Results) that the action level is based on the measurement Minimum Detectable Count Rate (MDCR) plus background in accordance with the FSS plan. Additionally, NRC staff noted that a Gross Gamma Action Level is presented in Table 8 (Action Levels for Survey Unit) as a pCi/g value based upon 50 percent of the normalized surrogate adjusted DCGL of 3.494 pCi/g for gamma-emitting ROC. The licensee further notes that in accordance with ZionSolutions TSD 11-004, Ludlum Model 44-10 Detector Sensitivity, the scan MDC was sufficient to detect residual radioactivity at the adjusted gross gamma action level of 1.747 pCi/g. It is important to note that field scanning instruments will not be measuring values as pCi/g, so the licensee should be clearer on the actual field scanning levels (in cpm) that would trigger an investigation and how those levels compare to the DCGL. It would also be useful for the licensee to clarify how field scanning levels were determined in accordance with the referenced TSD 11-004 document.
In multiple reports, it appears that some of the values listed in Table 1 (Statistical Quantities for Cs-137 and Co-60 from the) are different in Revision 1 of these release records than they were in the original Revision 0 version. There are no change bars or other indications of changes included in the Revision 1 documents. The licensee should ensure that changes between reports are clearly described.
In the release record for Survey Unit 10205 the value for sigma (0.012) used in Equation 5, and shown elsewhere in the document, does not match the value (0.08) listed in the paragraph above Equation 5. This does not affect the licensees final determination of the relative shift, but it is noted here for QA/QC considerations.
4.0 CONCLUSION
NRC staff concludes that the survey results presented in the Revised Final Status Survey Reports for Phase 1 are adequate to provide reasonable assurance that the licensee is able to demonstrate compliance with the unrestricted release criteria of Section 20.1402 of Title 10 of the Code of Federal Regulations.
Principal Contributors: John Clements, NMSS John Hickman, NMSS